no i dont think theres an orthodox belief that you need to have jewish ancestry to convert what the belief is that converts are jewish in our past lives but were reincarnated into a nonjewish body for numerous reasons most common being living an unjewish life in the last life even though a convert has been born into a nonjewish body the converts soul has always been jewish and just needs a proper beit din to affirm the jewishness of the convert having jewish ancestry has relevance or whatsoever unless if your mother and everyone along her maternal line were jewish